• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.5
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• pp.76-81
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• 2014

The Engineering ceramics have some excellent properties as materials for modern mechanical and electrical components. It is, however, not easy to polish them efficiently because they are strong and hard. This study is carried out to obtain a mirror surface on engineering ceramics by surperfinishing with high efficiency. To achieve this, we conducted a series of polishing experiments using representative engineering ceramics, such as $Al_2O_3$, SiC, $Si_3N_4$ and $ZrO_2$, using diamond abrasive film from the perspective of oscillations peed, the rotational speed of the workpiece, contact roller hardness, contact pressure and feed rate. Furthermore, the polishing efficiency and characteristics for engineering ceramics are discussed on the basis of optimal polishing time and surface roughness. Our results confirmed that efficient superfinishing conditions and polishing characteristics of engineering ceramics can be determined.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.8 s.173
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• pp.27-33
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• 2005

Polishing pads play an important role in chemical mechanical polishing(CMP) which has recently been recognized at the most effective method to achieve global planarization. In this paper, we have investigated CMP characteristics as a change of groove density of polishing pads. The parameter $(K_n)$ is proposed to estimate groove density of pad. The $K_n$ is defined as groove area divided by pitch area. As the groove density value increased, removal rate increased to some point and then gradually saturated in case of increasing the groove density excessively. In addition Within wafer non-uniformity(WIWNU) worse as groove density increased excessively, although WIWNU improved as groove density increased. Also the uniformity of temperature of pad surface decreased as the groove density increased. It was because that the cooling effect increased as groove density increased. In other words, increasing the groove density which means the apparent contact area of pad has influence on amount of discharge of slurry during polishing process.

• Journal of IKEEE
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• v.18 no.4
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• pp.456-462
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• 2014

Scintillators were polished in four steps using polishing paper, to reduce the optical loss occurring at their cross section when radiation detectors are fabricated with plastic scintillators. We studied the correlation between the polishing steps and detection efficiency and assessed the detection characteristics that are dependent in the polishing steps. Our results showed that the detection efficiency increased by approximately 7.75 times for a detector that used a scintillator polished in four steps, compared to a detector that used an depolished scintillator. For detectors fabricated using scintillators polished in different steps, better detection characteristics were obtained in terms of the activity, distance, and location of radiation, compared to detectors fabricated with an depolished scintillator.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.3
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• pp.53-60
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• 2004

We have developed and manufactured an experimental ultrasonic polishing machine with frequency of 20kHz at the power of vibration 1.7㎾ for effective ultrasonic polishing in processing of high hardness material. Design of the horn is performed by the FEM analysis. The following conclusions were empirically deduced through experimental results to clarify the major elements which affect the surface roughness during the ultrasonic process by following the experimental plans. The ultrasonic polishing machine has been developed in parts of structure part, ultrasonic generator, vibrator. We were able to process the high hardness material without difficulty as a result of ultrasonic polishing by utilizing the groove added step-type horn. Through analyzing by applying the experimental plans, the rotating speed of the horn was determined to be the major factor in influencing the surface roughness. In the case of ceramic, wafer, we were able to obtain good surface roughness when the feed rate and the ultrasonic output were higher. Because the load on slurry particle increases when the ultrasonic output is higher, the processed surface becomes worse in the case of optical glass.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.2
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• pp.144-151
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• 2012

Polishing is not only one of the most frequently adopted processes in modern industries, but also the most critical one to the surface quality of the products such as semi conductor wafers and LED sapphire wafers. With the required specifications for the wafer surface quality getting more and more strengthened, the manufacturers are spending huge amount of cost to renew the machine to meet the enhanced surface specifications. Surface qualities of the wafers are mostly damaged by the structural vibrations of the polishing machines. In this paper, the dynamic characteristics of a wafer polishing machine have been analyzed through the frequency response test and the computer simulation. And the supporting structure of a polishing machine has been investigated to minimize the vibration transmissions, to improve the stability of the machine and further to reduce the defects of the polished products. The result of the study shows that simple design modifications of the supporting structure without altering the main structure of the machine can substantially suppress the vibrations of the machine with negligible expenses.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.2
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• pp.1-6
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• 2008

In recent years, developments in the semiconductor and electronic industries have brought a rapid increase in the use of large size silicon wafer. For further improvement of the ultra precision surface and flatness of Si wafer necessary to high density ULSI, it is known that polishing is very important. However, most of these investigation was experiment less than 300mm diameter. Polishing is one of the important methods in manufacturing of Si wafers and in thinning of completed device wafers. This study reports the machining variables that has major influence on the characteristic of wafer polishing. It was adapted to polishing pressure, machining speed, and the slurry mix ratio, the optimum condition is selected by ultra precision wafer polishing using load cell and infrared temperature sensor. The optimum machining condition is selected a result data that use a pressure and table speed data. By using optimum condition, it achieves a ultra precision mirror like surface.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.609-613
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• 2004

On this study, electrochemical polishing is adapted to ultra-fine surface for semiconductor large radius gas-tube. The system which buffing and electrochemical polishing can be performed simultaneously was constructed in connection with developing exclusive system. Based on existing papers and the research of background, electrode gap and electrolyte flow were fixed. Current density and electrochemical precision time were chosen as variables. On this study, it is objected to find optimal precision condition and precision variables on the in-process electrochemical polishing.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.2
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• pp.26-32
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• 2010

This paper reports some experimental result in grinding and polishing of silicon cathodes used in semiconductor manufacturing process. Cup shape diamond core wheels were used in experiments and the radial and tangential grinding forces were measured with surface roughness. In polishing experiments, flat type and donut type wool polishing tools were tested. The experimental results indicate that the grinding forces are proportional to the material removal rates and the surface roughness are inversely proportional to the spindle speed. The surface roughness of polished Si decreases with polishing time and higher spindle speed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.8 no.1
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• pp.77-82
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• 2009

This paper reports a kinematic analysis and experimental results for the polishing process of G7 LCD glass. A kinematic analysis for the relative motion of the upper plate and lower plate has been done and computer simulation has been programmed. A series of polishing experiments has also been carried out and compared with analytical data. The experimental results agreed well with analytical ones. The experimental results indicate that the polishing removal is proportional to the relative speed and pressure.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.4
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• pp.73-78
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• 2002

This paper presents a neural network approach to estimate the surface roughness by considering the relationship between the polishing operation parameters and the surface roughness. The neural network model predicts the post-machining surface roughness by using several factors such as pre-machining surface roughness, pressure, feed rate, spindle speed, and the number of polishing as inputs. In this paper, the several neural network models are implemented to estimate the surface roughness by using actual experimental data. The experimental results show that the neural network approach is more appropriate to represent the polishing characteristics of mold and die compared with the results obtained by the approach using exponential function.